Wakeup receiver and system using frequency shift keying and shifted-frequency retransmission

A wireless device operative in a wireless communication network comprising:

• a primary receiver circuit adapted to be suspended to conserve power, and further adapted to resume operation if data demodulated from a received FSK wakeup signal identifies the wireless device;
• a limited-function, low-power wakeup receiver circuit adapted to receive a wakeup signal transmitted by the network at a first frequency, the wakeup signal being transmitted using Frequency Shift Keying (FSK), wherein a state of an information bit is encoded as a positive or negative offset from the first frequency, the wakeup receiver circuit comprising:
• a digitally controlled oscillator adapted to generate a local oscillator signal;
• a mixer adapted to frequency down-convert the wake-up signal from the first frequency to a second frequency lower than the first frequency;
• and
• a demodulator comprising first and second matched filters in the discrete time domain, wherein the first filter is configured to detect odd numbered members of an ordered set of equidistant frequencies, and reject even numbered ones, a separation between two frequencies in the ordered set being equal to two times the offset frequency of the FSK signal, and wherein the second filter is configured to detect even numbered members of the ordered set and reject odd numbered ones, thereby demodulating data modulated onto the FSK wakeup signal.

A method of operating a base station serving one or more low-power wireless devices in a wireless communication network, comprising:

• generating a first wakeup signal at a first frequency directed to a wireless device or group of wireless devices, the first wakeup signal being transmitted using Frequency Shift Keying (FSK), wherein a state of an information bit is encoded as a positive or negative frequency offset from the first frequency;
• transmitting the first FSK wakeup signal;
• generating a second FSK wakeup signal at a second frequency directed to the same wireless device or group of wireless devices, shifted from the first FSK wakeup signal frequency;
• and
• transmitting the second FSK wakeup signal after transmitting the first FSK wakeup signal.

A base station operative to serve one or more low-power wireless devices in a wireless communication network, comprising:

• a transceiver;
• and
• processing circuitry operatively connected to the transceiver, and adapted to
• generate a first wakeup signal at a first frequency directed to a wireless device or group of wireless devices, the first wakeup signal being transmitted using Frequency Shift Keying (FSK), wherein a state of an information bit is encoded as a positive or negative frequency offset from the first frequency;
• transmit the first FSK wakeup signal;
• generate a second FSK wakeup signal at a second frequency directed to the same wireless device or group of wireless devices, shifted from the first FSK wakeup signal frequency;
• and
• transmit the second FSK wakeup signal after transmitting the first FSK wakeup signal.